1. Field of the Invention
The invention relates to a process for evaluating motion signals in three-dimensional space and to a device for implementing the process.
The problems of the conventional processes described below are solved by a process for evaluating motion signals in three-dimensional space by using at least three acceleration sensors. The process includes the steps of obtaining a first initial measurement value in a first initial direction in space, the first initial measurement value being a first determined value, the first initial direction being a first desired direction in space; obtaining a second initial measurement value in a second initial direction in space, the second initial direction being different from the first initial direction; calculating a second desired direction in space and a second determined value from the first initial measurement value and the second initial measurement value, the second desired direction being different from each of the first initial direction and the second initial direction; calculating a third desired direction in space and a third determined value from the first initial measurement value and the second determined value, the third desired direction being different from each of the first desired direction and the second desired direction; and converting the first determined value, the second determined value and the third determined value into a first acceleration value in the first desired direction, a second acceleration value in the second desired direction and a third acceleration value in the third desired direction, respectively. The problems of the conventional devices described below are solved by a device for evaluating motion signals in three-dimensional space. The device includes a carrier element, and at least one of an acceleration sensor and a rotational angle/speed sensor. The at least one of an acceleration sensor and a rotational angle/speed sensor is attached to the carrier element.
The invention relates to a device for measuring motion. The device detects motion in space by means of several motion sensors. The measurement values for at least one direction of motion are processed together with the measurement values for at least one other direction of motion. An angular velocity measurement is combined with a linear acceleration measurement. Three linear acceleration measurements are combined to convert the accelerations into three corrected directions in space. A transformation of this type is useful when it is difficult to attach the sensors so that they are aligned with the directions in space to be measured, which is true especially in the case of measurements on the human body. According to the present process, the acceleration sensors can be attached anywhere; the desired directions are determined on the basis of two initial positions.
2. Description of the Related Art
The gait cycle during a stride is a complex process. The feet are highly complicated structures, each consisting of 26 bones and 31 joints, and they not only carry the human body but also provide elastic suspension for it when shocks occur during walking. They also hold us in a state of balance and sense irregularities in the ground. One feature of the human gait cycle is pronation, which is the inward rotation of the ankle during the gait cycle. Overpronation, that is, too much pronation, is often associated with complaints by runners. Many running shoes are therefore offered with medial supports, which are intended to prevent excessive pronation. Conversely, the use of a pronation support is inappropriate in the presence of underpronation (supination) and is considered a cause of complaints in its own right. Various aids and devices are therefore used to measure pronation in athletes.
Video analysis is often used as a basis for offering advice about running shoes. The customer is recorded by a video system as he is running on a treadmill. The video is then played back at very slow speed. The more-or-less normal pronation movement of the foot as it makes contact can be seen. Because this movement is easy to recognize and because excessive pronation can lead to complaints, the shoe which is recommended is the one with which the customer shows the least pronation.
Measurement on the treadmill suffers from several disadvantages: First, the required equipment is expensive and occupies a great deal of space. Second, running on a treadmill is not easy and changes the runner's normal running style. In any case, inexperienced customers require full attention. Third, the method itself is highly controversial on scientific grounds because of its inaccuracy. Fourth, the normal pronation movement, which is important for good health, is often overcompensated. Nevertheless, this method is widely used in stores specializing in running shoes.
There are also a few systems which detect the motion of the bare foot as it makes contact with pressure-measuring plates. This dynamic measuring method confronts the user with an additional difficulty, namely, the difficulty of stepping on the relatively small measuring platform at all while making a normal stride. Pressure-measuring plates are also relatively expensive, and a reliable evaluation of the pressure data can be accomplished only by sports scientists.
The company Currex offers a software program called “MotionQuest” to help with the selection of shoes. After various biomechanical data have been entered, the program searches a database for a suitable shoe. The MotionQube Station from Currex makes it easier to enter the data by the use of a scanner. This technology with a scanner is also offered by Rothballer.
Scanners are also sold with a different type of software, which takes into account only the shape of the sole. This program is sold under the name “FootPrint” by Schmitzl Systems and is also used at Runners Point. Many specialty shops arrange “campaign days”, in which measurement systems from certain shoe manufacturers (for example, the Footscan System from Adidas or scanners from Asics) are used.